In heat pump systems, the volume ratio is the internal volume of the outdoor coil versus the internal volume of the indoor coil. The indoor and outdoor coils in conventional heat pump systems are of the appropriate size to run efficiently in cooling and heating mode. When upgrading older heat pump systems from a low SEER rating to SEER 13 or higher in order to improve cooling performance, an imbalance can occur as the volume ratio changes. When the indoor coil volume is smaller than the outdoor coil volume, the system has a high volume ratio. Conversely, when the indoor coil volume is greater than the outdoor coil volume, the system has a low volume ratio. These conditions create an imbalance in the amount of refrigerant charge needed as the heat pump changes from heating to cooling mode, i.e., the system needs more refrigerant during the cooling cycle than during the heating cycle. Existing charge compensators comprise a tank with a vapor tube passing through the tank, but the vapor tube is not open to the tank. The tank inner volume is connected to the liquid line and the excess charge is thermally drawn into the tank when the tube is cold during the heating mode; the charge is thermally driven out during the cooling mode when the tube is warm during the cooling mode. This type of compensator, if used in the field, must be brazed into the system to assure that the system is vapor tight. This requires that the refrigerant charge be removed, the system be opened, the compensator brazed in place by a technician, and the total system be evacuated and recharged.
Accordingly, what is needed in the art is a charge compensator that does not require brazing the compensator into the liquid and vapor lines.